Nowadays, with the provision of international roaming service, a subscriber to a mobile communication service such as domestic Wideband Code Division Multiple Access (WCDMA) accesses a domestic home network using the same mobile communication terminal even from abroad and is then capable of using various types of mobile communication services, for example, voice or video call service, multimedia data download/upload service, wireless Internet service, etc.
Generally, when international roaming service subscriber accesses a domestic home network from abroad, he or she presses numbers corresponding to ‘International access code (1)+country code (82)+area code (010, 019, 02, 041, etc.) except the first number ‘0’+phone number (****-####)’, and presses a send button, thus using a call or messaging service.
In this case, in a Global System for Mobile Telecommunication (GSM)/WCDMA network, a “+” key may be occasionally used as an international access code. That is, “+”+“country code”+“area code except the first number 0” may be entered.
Further, when international roaming service subscriber accesses a network belonging to his or her country from abroad, he or she presses ‘area code+phone number’ and then presses a send button similar to a method using the service of a domestic network, thus using a call or messaging service.
When a home network is accessed from a foreign network in this way, the Mobile Switching Center (MSC) of the foreign network basically analyzes a called number and outputs an Integrated Services Digital Network (ISDN) User part (ISUP) call to the home network via the network of an international line service provider in the foreign network. When the ISUP call is received through the home network, the MSC of the home network queries a Home Location Register (HLR), which manages the location of a subscriber corresponding to the called number, about a routing number through a Mobile Application Part (MAP), receives the routing number, and connects the ISUP call to a called MSC using the received routing number.
Generally, the mobile communication terminal number of a subscriber is a unique identification number assigned to the mobile communication terminal of each subscriber through both an International Mobile Subscriber Identity (IMSI) number, managed by an Universal Subscriber Identity Module (USIM) card mounted on the mobile communication terminal, and a Mobile Subscriber Integrated Service Digital Network (MSISDN) number, assigned by the home network to the subscriber terminal to correspond to the IMSI number.
In particular, since a GSM/WCDMA-type mobile communication terminal can support a multi-band operation, automatic roaming is possible. Services for assigning a plurality of MSISDN numbers to a single IMSI using the characteristics of the GSM/WCDMA-type mobile communication terminal and applying the MSISDN numbers to automatic roaming have been developed. One of these services is a Single IMSI Multiple Number (SIMN) service.
That is, in such an SIMN service, a home network assigns a primary number (primary no.) to correspond to the IMSI of a subscriber mobile communication terminal, and a partner network, which concludes an agreement with the home network, assigns a secondary number (secondary no.), so that the primary and secondary numbers are applied to automatic roaming.
However, when a mobile communication subscriber who has subscribed to such an SIMN service uses international roaming service, there is a need to precisely define a method of processing an originating call depending on whether the mobile communication subscriber originates a call using the primary no. of the home network or using the secondary no. of the partner network.
Meanwhile, in a conventional outbound international roaming service, since call origination and call reception are performed using only a single MSISDN number assigned by the home network, there is a need to always identify a subscriber via the home network and perform other types of roaming logic at the time of processing calls. Accordingly, even when a called subscriber is located in the same foreign network as a network in which an outbound roamer is located, an international line between the home network and the foreign network is used, so that there is a problem in that unnecessary charges occur, thus causing a user to pay high charges.
Therefore, a system capable of efficiently supporting an international automatic roaming service profitable for the location of the subscriber, such as by allowing a relevant outbound roamer to be provided with an inexpensive international roaming service when a mobile communication subscriber who has subscribed to an SIMN service uses an outbound international roaming service, is required.